Improved hydrogen storage kinetics of MgH2 using TiFe0.92Mn0.04Co0.04 with in-situ generated α-Fe as catalyst

While TiFe alloy has recently attracted attention as the efficient catalyst to enhance de/hydrogenation rates of Mg/MgH₂, the difficulty of its activation characteristics has hindered further improvement of reaction kinetics. Herein, we report that the TiFe_0.92Mn_0.04Co_0.04 catalyst can overcome the abovementioned challenges. The synthesized MgH₂-30 wt% TiFe_0.92Mn_0.04Co_0.04 can release 4.5 wt% of hydrogen in 16 min at 250 °C, three times as fast as MgH₂. The activation energy of dehydrogenation was as low as 84.6 kJ mol⁻¹, which is 46.8% reduced from pure MgH₂. No clear degradation of reaction rates and hydrogen storage capacity was observed for at least 30 cycles. Structural studies reveal that TiFe_0.92Mn_0.04Co_0.04 partially decomposes to in-situ generated α-Fe particles dispersed on TiFe_0.92Mn_0.04Co_0.04. The presence of α-Fe reduces the formation of an oxide layer on TiFe_0.92Mn_0.04Co_0.04, enabling the activation processes. At the same time, the hydrogen incorporation capabilities of TiFe_0.92Mn_0.04Co_0.04 can provide more hydrogen diffusion paths, which promote hydrogen dissociation and diffusion. These discoveries demonstrate the advanced nature and importance of combining the in-situ generated α-Fe with TiFe_0.92Mn_0.04Co_0.04. It provides a new strategy for designing highly efficient and stable catalysts for Mg-based hydrogen storage materials.